非线性随机车流-自锚式悬索桥耦合振动分析系统

Analytic System of Nonlinear Random Traffic Flow-self-anchored Suspension Bridge Coupling Vibration

自锚式悬索桥独特的锚固形式使其主梁承受主缆传递的巨大轴向压力,为了研究主梁刚度在初内力及活载作用下的弱化问题对自锚式悬索桥结构静动力响应的影响,首先,结合自锚式悬索桥的非线性特点引入初应力刚度矩阵,考虑随机车流过桥时几何非线性的时变性,采用分离迭代法建立非线性随机车流-自锚式悬索桥耦合振动分析系统,并编制相应的非线性分析模块。其次,以某三跨混凝土自锚式悬索桥为例,选取集中力匀速过桥工况,利用ANSYS软件对非线性分析模块的可靠性进行验证。最后,分别设置2种极端工况:第1种是单车工况,近似认为只有恒载作用下产生的几何非线性;第2种是密集交通流工况,认为是恒载和最不利活载共同作用产生的几何非线性,并采用元胞自动机模型对密集车流进行模拟,研究自锚式悬索桥恒载和活载初内力引起的几何非线性对桥梁响应的影响程度。研究结果表明:单车工况下,梁塔恒载初内力对自锚式悬索桥的车辆过桥结构响应影响显著,主梁和主塔初内力贡献程度明显不同,主梁初内力对结构刚度矩阵变化的影响贡献较大而主塔贡献微小;相对于恒载,密集车流作用下初内力效应引起的几何非线性对自锚式悬索桥结构刚度影响微小,对结构响应的非线性影响也不明显。

Self-anchored suspension bridges have the unique anchoring form where the main girder bears huge axial pressure from the main cable.In this paper,the influence of the main beam stiffness-weakening problem on self-anchored suspension bridge static dynamic response under the initial internal force and live was studied.Firstly,a coupled vibration analysis system of the nonlinear random traffic flow-self-anchored suspension bridge based on discrete iterative method was developed,and the corresponding nonlinear analysis module was prepared.In order to achieve the goal,we have combined the nonlinear characteristic of the bridge with the initial stress stiffness matrix introduced and also considered the geometric nonlinear time-variation whenthe random traffic flow passes through the bridge.Secondly,considering a three-span concrete self-anchored suspension bridge as an example of the concentrated force across the bridge with constant speed,the reliability of nonlinear analysis module was verified using ANSYS.Finally,two extreme conditions were studied;＂single vehicle＂case was considered the geometrical nonlinearity only under dead load,and＂dense traffic flow＂case was considered as dead load and live load.The cellular automata model was used to simulate dense traffic flow to study the bridge response influence of the geometric nonlinearity caused by the initial internal force of the dead and live loads.The results suggest that the dead load initial internal forces of the main girder and the main tower have a great effect on structural response with a significantly different degree of contribution.Also,it is shown that the initial internal force of the main girder contributes significantly to the change of the structural stiffness matrix,but not much contribution of the main tower towards the same.We conclude that compared to the dead load,the geometrical nonlinearity caused by initial internal force under the dense traffic flow has little influence on the stiffness of the self-anchored suspension bridge and the nonlinear structural response.